Washington (CNN) -- A new order from the general in charge of U.S. troops in northern Iraq makes getting pregnant or impregnating a fellow soldier an offense punishable by court-martial.

The directive, part of a larger order restricting the behavior of the 22,000 soldiers under Maj. Gen. Anthony Cucolo's command, is meant to prevent losing soldiers at a time when troop strength is stretched thin, Cucolo explained in a statement sent to the troops under his command and provided to CNN.

"I need every soldier I've got, especially since we are facing a drawdown of forces during our mission," Cucolo wrote. "Anyone who leaves this fight earlier than the expected 12-month deployment creates a burden on their teammates. Anyone who leaves this fight early because they made a personal choice that changed their medical status -- or contributes to doing that to another -- is not in keeping with a key element of our ethos."

The rule, enacted November 4, was first reported by Stars and Stripes, a military-focused publication. It prohibits "becoming nondeployable for reasons within the control of the soldier," which include "becoming pregnant, or impregnating a soldier ... resulting in the redeployment of the pregnant soldier."

Pregnancy that arises from sexual assault would not be punished, Cucolo said.

The directive applies to all military and civilians serving under Cucolo in northern Iraq, an area that includes Balad, Kirkuk, Tikrit, Mosul and Samarra, according to the Web site of Multi-National Force Iraq.

Of the 22,000 people under Cucolo's command, 1,682 are women.

Cucolo will decide what cases will be pursued.

"I am the only individual who passes judgment on these cases. I decide every case based on the unique facts of each soldier's situation," Cucolo wrote in his explanation of the new rules.

Cucolo said he considers his female soldiers "invaluable" and he wants to ensure they fulfill their deployments.

"I am responsible and accountable for the fighting ability of this outfit. I am going to do everything I can to keep my combat power -- and in the Army, combat power is the individual soldier," his statement said. "To this end, I made an existing policy stricter. I wanted to encourage my soldiers to think before they acted, and understand their behavior and actions have consequences -- all of their behavior."

In an e-mail to CNN, Cucolo stressed the rule "is just a small part of a general policy on behavior and actions," and is "lawful."

The memo outlines a long list of behaviors that are prohibited, from gambling and using drugs to behaviors that would offend Iraqis, such as entering a mosque or religious site unless "required by military necessity."

While the rules may seem unusual to some, they are not out of line with how the military regulates behavior to a much stricter degree than the general public is used to, said Eugene Fidell, who teaches military law at Yale University.

"Questions of personal autonomy play out differently in the military," Fidell said.

He said the purpose of the rule is mostly to have a "chilling effect" on behavior, but he doubts it would ever be fully prosecuted. If it were, however, it appears to be legal, he said.

"If push came to shove and there was prosecution, I think the rule would be upheld as a reasonable balance of the competing interests," he said.

It is not without precedent, Fidell said. During the Vietnam War, a female troop would be discharged for getting pregnant. That rule was challenged, but the government did not want to defend it at the time.

According to the explanation of the policy that was sent to all those affected, only a few cases have been considered for punishment under the new rules. Four soldiers have gotten pregnant since Cucolo took over command of northern Iraq operations at the beginning of November, he told CNN in an e-mail. Of the eight soldiers involved, none were court-martialed. Instead, all received a written reprimand, Cucolo said.

In one case, a male soldier received the "most severe punishment," according to the explanation sent to those serving in northern Iraq. Cucolo does not give any other details about the case except to say the soldier "committed adultery as well."